What acid does aluminum not react with? What is aluminum

For the first time, aluminum was obtained only at the beginning of the 19th century. This was done by the physicist Hans Oersted. He conducted his experiment with potassium amalgam, aluminum chloride and.

By the way, the name of this silvery material comes from the Latin word "alum", because this element is extracted from them.

Alum is a natural metal-based mineral that combines salts of sulfuric acid in its composition.

Used to be considered precious metal and cost an order of magnitude more expensive than gold. This was explained by the fact that the metal was quite difficult to separate from impurities. So only rich and influential people could afford aluminum jewelry.

But in 1886, Charles Hall came up with a method for mining aluminum on an industrial scale, which dramatically reduced the cost of this metal and allowed it to be used in metallurgical production. The industrial method consisted in the electrolysis of a cryolite melt in which aluminum oxide was dissolved.

Aluminum is a very popular metal, because many things that a person uses in everyday life are made from it.

Application of aluminum

Due to its malleability and lightness, as well as its resistance to corrosion, aluminum is a valuable metal in modern industry. Aluminum is used not only for kitchen utensils - it is widely used in auto and aircraft construction.

Also, aluminum is one of the most inexpensive and economical materials, as it can be used indefinitely by melting down unnecessary aluminum items, such as cans.

Metallic aluminum is safe, but its compounds can be toxic to humans and animals (especially aluminum chloride, acetate, and aluminum sulfate).

Physical properties of aluminum

Aluminum is a fairly light, silvery metal that can form alloys with most metals, especially copper, and silicon. It is also very plastic, it can easily be turned into a thin plate or foil. The melting point of aluminum = 660 °C and the boiling point is 2470 °C.

Chemical properties of aluminum

At room temperature, the metal is coated with a strong Al₂O₃ aluminum oxide film, which protects it from corrosion.

Aluminum practically does not react with oxidizing agents due to the oxide film protecting it. However, it can be easily destroyed so that the metal exhibits active reducing properties. It is possible to destroy the aluminum oxide film with a solution or melt of alkalis, acids, or with the help of mercury chloride.

Due to its reducing properties, aluminum has found application in industry - for the production of other metals. This process is called aluminothermy. This feature of aluminum is in the interaction with oxides of other metals.

For example, consider the reaction with chromium oxide:

Cr₂O₃ + Al = Al₂O₃ + Cr.

Aluminum reacts well with simple substances. For example, with halogens (with the exception of fluorine), aluminum can form aluminum iodide, chloride, or aluminum bromide:

2Al + 3Cl₂ → 2AlCl₃

With other non-metals such as fluorine, sulfur, nitrogen, carbon, etc. aluminum can only react when heated.

Silver metal also reacts with complex chemicals. For example, with alkalis, it forms aluminates, that is, complex compounds that are actively used in the paper and textile industries. Moreover, it reacts as aluminum hydroxide

Al(OH)₃ + NaOH = Na),

and metallic aluminum or aluminum oxide:

2Al + 2NaOH + 6Н₂О = 2Na + ЗН₂.

Al₂O₃ + 2NaOH + 3H₂O = 2Na

With aggressive acids (for example, with sulfuric and hydrochloric), aluminum reacts quite calmly, without ignition.

If you lower a piece of metal into hydrochloric acid, then a slow reaction will begin - at first the oxide film will dissolve - but then it will accelerate. Aluminum dissolves in hydrochloric acid with the release of mercury for two minutes, and then rinse it well. The result is an amalgam, an alloy of mercury and aluminum:

3HgCI₂ + 2Al = 2AlCI₃ + 3Hg

Moreover, it is not held on the surface of the metal. Now, by lowering the purified metal into water, one can observe a slow reaction, which is accompanied by the evolution of hydrogen and the formation of aluminum hydroxide:

2Al + 6H₂O = 2Al(OH)₃ + 3H₂.

One of the most common elements on the planet is aluminum. The physical and chemical properties of aluminum are used in industry. Everything you need to know about this metal you will find in our article.

The structure of the atom

Aluminum is the 13th element of the periodic table. He is in the third period, III group, the main subgroup.

The properties and uses of aluminum are related to its electronic structure. The aluminum atom has a positively charged nucleus (+13) and 13 negatively charged electrons located on three energy levels. The electronic configuration of an atom is 1s 2 2s 2 2p 6 3s 2 3p 1.

There are three electrons on the outer energy level, which determine the constant valency III. In reactions with substances, aluminum enters an excited state and is able to donate all three electrons, forming covalent bonds. Like other active metals, aluminum is a powerful reducing agent.

Rice. 1. The structure of the aluminum atom.

Aluminum is an amphoteric metal that forms amphoteric oxides and hydroxides. Depending on the conditions, the compounds exhibit acidic or basic properties.

Physical Description

Aluminum has:

• lightness (density 2.7 g / cm 3);
• silver grey;
• high electrical conductivity;
• malleability;
• plasticity;
• melting point - 658°C;
• boiling point - 2518.8 ° C.

Tin containers, foil, wire, alloys are made from metal. Aluminum is used in the manufacture of microcircuits, mirrors, and composite materials.

Rice. 2. Tin containers.

Aluminum is paramagnetic. Metal is attracted to a magnet only in the presence of a magnetic field.

Chemical properties

In air, aluminum quickly oxidizes, becoming covered with an oxide film. It protects the metal from corrosion, and also prevents interaction with concentrated acids (nitric, sulfuric). Therefore, acids are stored and transported in aluminum containers.

Under normal conditions, reactions with aluminum are possible only after the removal of the oxide film. Most reactions take place at high temperatures.

The main chemical properties of the element are described in the table.

Aluminum does not react directly with hydrogen. Reaction with water is possible after removal of the oxide film.

Rice. 3. Reaction of aluminum with water.

What have we learned?

Aluminum is an amphoteric active metal with constant valency. It has a low density, high electrical conductivity, plasticity. Attracted by a magnet only in the presence of a magnetic field. Aluminum reacts with oxygen, forming a protective film that prevents reactions with water, concentrated nitric and sulfuric acids. When heated, it interacts with non-metals and concentrated acids, under normal conditions - with halogens and dilute acids. In oxides, it displaces less active metals. Does not react with hydrogen.

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Aluminum - destruction of metal under the influence of the environment.

For the reaction Al 3+ + 3e → Al, the standard electrode potential of aluminum is -1.66 V.

The melting point of aluminum is 660 °C.

The density of aluminum is 2.6989 g / cm 3 (under normal conditions).

Aluminum, although it is an active metal, has fairly good corrosion properties. This can be explained by the ability to be passivated in many aggressive environments.

The corrosion resistance of aluminum depends on many factors: the purity of the metal, the corrosive environment, the concentration of aggressive impurities in the environment, temperature, etc. The pH of solutions has a strong influence. Aluminum oxide on the metal surface is formed only in the pH range from 3 to 9!

Its purity greatly affects the corrosion resistance of Al. For the manufacture of chemical aggregates, equipment, only high-purity metal (without impurities) is used, for example, aluminum grades AB1 and AB2.

Corrosion of aluminum is not observed only in those environments where a protective oxide film is formed on the metal surface.

When heated, aluminum can react with some non-metals:

2Al + N 2 → 2AlN - interaction of aluminum and nitrogen with the formation of aluminum nitride;

4Al + 3С → Al 4 С 3 - reaction of interaction of aluminum with carbon with the formation of aluminum carbide;

2Al + 3S → Al 2 S 3 - the interaction of aluminum and sulfur with the formation of aluminum sulfide.

Corrosion of aluminum in air (atmospheric corrosion of aluminum)

Aluminum, when interacting with air, passes into a passive state. When pure metal comes into contact with air, a thin protective film of aluminum oxide instantly appears on the aluminum surface. Further, the growth of the film slows down. The formula of aluminum oxide is Al 2 O 3 or Al 2 O 3 H 2 O.

The reaction of interaction of aluminum with oxygen:

4Al + 3O 2 → 2Al 2 O 3 .

The thickness of this oxide film is between 5 and 100 nm (depending on operating conditions). Aluminum oxide has good adhesion to the surface, satisfies the condition of the continuity of oxide films. When stored in a warehouse, the thickness of aluminum oxide on the metal surface is about 0.01 - 0.02 microns. When interacting with dry oxygen - 0.02 - 0.04 microns. During heat treatment of aluminum, the thickness of the oxide film can reach 0.1 µm.

Aluminum is quite resistant both in clean rural air and in an industrial atmosphere (containing sulfur vapor, hydrogen sulfide, gaseous ammonia, dry hydrogen chloride, etc.). Because aluminum corrosion in gaseous media is not affected by sulfur compounds - it is used for the manufacture of sour oil processing plants, rubber vulcanization devices.

Corrosion of aluminum in water

Corrosion of aluminum is almost not observed when interacting with clean fresh, distilled water. Increasing the temperature to 180 °C has no particular effect. Hot water vapor also has no effect on aluminum corrosion. If a little alkali is added to water, even at room temperature, the rate of aluminum corrosion in such an environment will slightly increase.

The interaction of pure aluminum (not coated with an oxide film) with water can be described using the reaction equation:

2Al + 6H 2 O \u003d 2Al (OH) 3 + 3H 2.

When interacting with sea water, pure aluminum begins to corrode, because. sensitive to dissolved salts. To exploit aluminum in sea water, a small amount of magnesium and silicon is introduced into its composition. Corrosion resistance of aluminum and its alloys, when exposed to sea ​​water, is significantly reduced if copper is included in the composition of the metal.

Corrosion of aluminum in acids

As the purity of aluminum increases, its resistance to acids increases.

Corrosion of aluminum in sulfuric acid

For aluminum and its alloys, sulfuric acid (it has oxidizing properties) of medium concentrations is very dangerous. The reaction with dilute sulfuric acid is described by the equation:

2Al + 3H 2 SO 4 (razb) → Al 2 (SO 4) 3 + 3H 2.

Concentrated cold sulfuric acid has no effect. And when heated, aluminum corrodes:

2Al + 6H 2 SO 4 (conc) → Al 2 (SO 4) 3 + 3SO 2 + 6H 2 O.

This forms a soluble salt - aluminum sulfate.

Al is stable in oleum (fuming sulfuric acid) at temperatures up to 200 °C. Due to this, it is used for the production of chlorosulfonic acid (HSO 3 Cl) and oleum.

Corrosion of aluminum in hydrochloric acid

In hydrochloric acid, aluminum or its alloys quickly dissolve (especially with increasing temperature). Corrosion equation:

2Al + 6HCl → 2AlCl 3 + 3H 2 .

Solutions of hydrobromic (HBr), hydrofluoric (HF) acids act similarly.

Corrosion of aluminum in nitric acid

A concentrated solution of nitric acid has high oxidizing properties. Aluminum in nitric acid at normal temperature is exceptionally stable (higher resistance than stainless steel 12X18H9). It is even used to produce concentrated nitric acid by direct synthesis.

When heated, the corrosion of aluminum in nitric acid proceeds according to the reaction:

Al + 6HNO 3 (conc) → Al(NO 3) 3 + 3NO 2 + 3H 2 O.

Corrosion of aluminum in acetic acid

Aluminum has a sufficiently high resistance to acetic acid of any concentration, but only if the temperature does not exceed 65 ° C. It is used for the production of formaldehyde and acetic acid. At higher temperatures, aluminum dissolves (with the exception of acid concentrations of 98 - 99.8%).

In bromine, weak solutions of chromic (up to 10%), phosphoric (up to 1%) acids at room temperature, aluminum is stable.

Citric, butyric, malic, tartaric, propionic acids, wine, fruit juices have a weak effect on aluminum and its alloys.

Oxalic, formic, organochlorine acids destroy the metal.

The corrosion resistance of aluminum is greatly affected by vaporous and droplet-liquid mercury. After a short contact, the metal and its alloys corrode intensively, forming amalgams.

Corrosion of aluminum in alkalis

Alkalis easily dissolve the protective oxide film on the surface of aluminum, it begins to react with water, as a result of which the metal dissolves with the release of hydrogen (corrosion of aluminum with hydrogen depolarization).

2Al + 2NaOH + 6H 2 O → 2Na + 3H 2;

2(NaOH H 2 O) + 2Al → 2NaAlO 2 + 3H 2.

aluminates are formed.

Also, the oxide film is destroyed by salts of mercury, copper and chloride ions.

1. Does not interact with H 2 .

2. How the active metal reacts with almost all non-metals without heating, if the oxide film is removed.

4Al + 3O 2 → 2Al 2 O 3

2Al + 3Cl 2 → 2AlCl 3

Al + P → AlP

3. Reacts with H 2 O:

Aluminum is an active metal with a high affinity for oxygen. In air, it is covered with a protective oxide film. If the film is destroyed, then aluminum actively interacts with water.

2Al + 6H 2 O \u003d 2Al (OH) 3 + 3H 2

4. With dilute acids:

2Al + 6HCl → 2AlCl 3 + 3H 2

2Al + 3H 2 SO 4 → Al 2 (SO 4) 3 + 3H 2

With concentrated HNO 3 and H 2 SO 4 does not react under normal conditions, but only when heated.

5. With alkalis:

2Al + 2NaOH 2NaAlO 2 + 3H 2

Aluminum forms complexes with aqueous solutions of alkalis:

2Al + 2NaOH + 10 H 2 O = 2Na + - + 3H 2

or Na,

Na 3 , Na 2- hydroxoaluminates. The product depends on the alkali concentration.

4Al + 3O 2 → 2Al 2 O 3

Al 2 O 3 (alumina) is found in nature in the form of corundum mineral (close to diamond in hardness). Gems ruby ​​and sapphire - also Al 2 O 3, colored with impurities of iron, chromium

Aluminium oxide- amphoteric. When fused with alkalis, salts of metaaluminum acid HAlO 2 are obtained. For example:

Also interacts with acids

white gelatinous precipitate aluminum hydroxide dissolves in acids

Al(OH) 3 + 3HCl = AlCl 3 + 3 H 2 O,

and in an excess of alkali solutions, exhibits amphoteric

Al(OH) 3 + NaOH + 2H 2 O = Na

When fused with alkalis, aluminum hydroxide forms salts of metaaluminum or orthoaluminum acids

Al (OH) 3 Al 2 O 3 + H 2 O

Aluminum salts are highly hydrolyzed. Salts of aluminum and weak acids are converted into basic salts or undergo complete hydrolysis:

AlCl 3 + HOH ↔ AlOHCl 2 + HCl

Al +3 + HOH ↔ AlOH +2 + H + pH>7 proceeds through stage I, but when heated, it can also proceed through stage II.

AlOHCl 2 + HOH ↔ Al(OH) 2 Cl + HCl

AlOH +2 + HOH ↔ Al(OH) 2 + + H +

When boiling, stage III can also occur

Al(OH) 2 Cl + HOH ↔ Al(OH) 3 + HCl

Al(OH) 2 + + HOH ↔ Al(OH) 3 + H +

Aluminum salts are highly soluble.

AlCl 3 - aluminum chloride is a catalyst in oil refining and various organic synthesis.

Al 2 (SO 4) 3 × 18H 2 O - aluminum sulfate is used to purify water from colloidal particles captured by Al (OH) 3 formed during hydrolysis and a decrease in hardness

Al 2 (SO 4) 3 + Ca (HCO 3) 2 \u003d Al (OH) 3 + CO 2 + CaSO 4 ↓

In the leather industry, it serves as a mordant when crumbling cotton fabrics - KAl (SO 4) 2 × 12H 2 O - potassium-aluminum sulfate (potassium alum).

The main application of aluminum is the production of alloys based on it. Duralumin is an alloy of aluminum, copper, magnesium and manganese.

Silumin - aluminum and silicon.

Their main advantage is low density, satisfactory resistance to atmospheric corrosion. Hulls of artificial earth satellites and spaceships are made from aluminum alloys.

Aluminum is used as a reducing agent in metal smelting (aluminothermy)

Cr 2 O 3 + 2 Al t \u003d 2Cr + Al 2 O 3.

Also used for thermite welding of metal products (a mixture of aluminum and iron oxide Fe 3 O 4) called thermite gives a temperature of about 3000 ° C.

aluminum oxide(alumina) A1 2 O 3, colorless. crystals; m.p. 2044°C; t. kip. 3530 °С. The only stable up to 2044 ° C crystalline. modification of aluminum oxide-A1 2 O 3 (corundum): rhombohedral lattice, a \u003d 0.512 nm, \u003d 55.25 ° (for hexagonal installation a \u003d 0.475 nm, c \u003d 1.299 nm, space group D 6 3d, z \u003d 2); dense 3.99 g / cm 3; N ° pl 111.4 kJ / mol; temperature dependence equations: heat capacity C ° p \u003d \u003d 114.4 + 12.9 * 10 -3 T - 34.3 * 10 5 T 2 JDmol * K) (298T 1800 K), vapor pressure Igp (Pa) \u003d -54800/7+1.68 (up to ~ 3500 K); temperature coefficient. linear expansion (7.2-8.6) * 10 -6 K -1 (300T1200 K); thermal conductivity sintered at 730°C sample 0.35 W/(mol*K); Mohs hardness 9; the refractive index for an ordinary beam is n 0 1.765, for an extraordinary beam it is 1.759.

Aluminum oxide (Al2O3) has an exceptional set of properties, such as:

• High hardness
• Good thermal conductivity
• Excellent corrosion resistance
• low density
• Strength retention over a wide temperature range
• electrical insulating properties
• Low cost compared to other ceramic materials

All these combinations make the material indispensable in the manufacture of corrosion-resistant, wear-resistant, electrically insulating and heat-resistant products for various industries.

Main applications:

• Lining of mills, hydrocyclones, concrete mixers, extruders, conveyors, pipes and other wear equipment
• Mechanical seal rings
• Dies, wires, guides
• Plain bearings, shafts and lining of wet parts of chemical pumps
• Grinding bodies
• Parts of papermaking equipment
• Burners
• Extruder nozzles (cores)
• crucibles
• Elements of valves and valves
• Nozzles for argon-arc welding machines
• electrical insulators

There are several modifications of aluminum oxide, depending on the content of the main phase and impurities, which are distinguished by strength and chemical resistance.

aluminum hydroxide

Aluminum hydroxide Al(OH) 3 is a colorless solid, insoluble in water, which is part of many bauxites. Exists in four polymorphic modifications. In the cold, α-Al (OH) 3 - bayerite is formed, and when deposited from a hot solution γ-Al (OH) 3 - gibbsite (hydargilite), both crystallize in a monoclinic syngony, have a layered structure, the layers consist of octahedrons, between the layers acts hydrogen bond. There is also triclinic gibbsite γ'-Al(OH) 3 , triclinic nordstrandite β-Al(OH) 3 and two modifications of AlOOH oxohydroxide - orthorhombic boehmite and diaspore. Amorphous aluminum hydroxide has a variable composition Al 2 O 3 nH 2 O. When heated above 180°C, it decomposes.

Chemical properties

Aluminum hydroxide is a typical amphoteric compound, freshly obtained hydroxide dissolves in acids and alkalis:

2Al(OH) 3 + 6HCl = 2AlCl 3 + 6H 2 O

Al(OH) 3 + NaOH + 2H 2 O = Na.

When heated, it decomposes, the dehydration process is rather complicated and can be schematically represented as follows:

Al(OH) 3 \u003d AlOOH + H 2 O;

2AlOOH \u003d Al 2 O 3 + H 2 O.

aluminum hydroxide - Chemical substance, which is a compound of aluminum oxide with water. It can be in liquid and solid states. Liquid hydroxide is a jelly-like transparent substance that is very poorly soluble in water. Solid hydroxide is a crystalline substance white color, which has passive chemical properties and does not react with almost any other element or compound.

aluminum chloride

Sublimates at 183°C under normal pressure (melts at 192.6°C under pressure). It is highly soluble in water (44.38 g in 100 g H 2 O at 25 ° C); due to hydrolysis, smokes in moist air, releasing HCl. Crystal hydrate AlCl 3 6H 2 O precipitates from aqueous solutions - yellowish-white deliquescent crystals. Well soluble in many organic compounds (in ethanol - 100 g in 100 g of alcohol at 25 ° C, in acetone, dichloroethane, ethylene glycol, nitrobenzene, carbon tetrachloride and etc.); however, it is practically insoluble in benzene and toluene.

aluminum sulfate

Aluminum sulfate is a white salt with a gray, blue or pink tint, under normal conditions exists in the form of crystalline Al 2 (SO 4) 3 18H 2 O - colorless crystals. When heated, it loses water without melting; when ignited, it decomposes into Al 2 O 3 and SO 3 and O 2. It dissolves well in water. Technical aluminum sulfate can be obtained by treating bauxite or clay with sulfuric acid, and a pure product by dissolving Al (OH) 3 in hot concentrated H 2 SO 4.

Aluminum sulfate is used as a coagulant for water purification for household and industrial purposes and for use in paper, textile, leather and other industries.

Used as food additive E-520

aluminum carbide

Aluminum carbide is obtained by direct reaction of aluminum with carbon in an arc furnace.

Iron with aluminum

Alni- a group of hard magnetic (high-coercivity) iron (Fe) - nickel (Ni) - aluminum (Al) alloys.

Alloying of alni alloys improves their magnetic characteristics, copper alloying is used (for example, an alloy of 24% nickel, 4% copper, 13% aluminum and 59% iron), cobalt (alnico and magnico alloys). The impurity of carbon reduces the magnetic properties of the alloy; its content should not exceed 0.03%.

Alni alloys are characterized by high hardness and brittleness, so casting is used to make permanent magnets from them.

sodium aluminate

sodium aluminate- an inorganic compound, a complex oxide of sodium and aluminum with the formula NaAlO 2, a white amorphous substance, reacts with water.

Orthoaluminic acid

Alumina "you, salts of aluminum acids: orthoaluminum H3 AlO3, metaaluminum HAlO2, etc. Aluminates of the general formula R are most common in nature, where R is Mg, Ca, Be, Zn, etc. Among them, there are: 1) octahedral varieties, so-called. spinels - Mg (noble spinel), Zn (ganite or zinc spinel), etc. and 2) rhombic varieties - Be (chrysoberyl), etc. (in the formulas minerals atoms that make up a structural group are usually enclosed in square brackets).

Alkali metal aluminates are obtained by reacting Al or Al (OH) 3 with caustic alkalis: Al (OH) 3 + KOH \u003d KAlO2 + 2H2 O. Of these, a sodium luminates NaAlO2, formed during the alkaline process of obtaining alumina , used in the textile industry as a stain. Aluminates of alkaline earth metals are obtained by fusing their oxides with Al2 O3; of these, calcium aluminates CaAl2 O4 serves as the main component of fast-hardening aluminous cement.

Aluminates of rare earth elements have gained practical importance. They are obtained by joint dissolution of oxides of rare earth elements R2 03 and Al(NO3)3 in nitric acid, evaporation of the resulting solution until the salts crystallize and calcination of the latter at 1000-1100°C. The formation of aluminates is controlled by X-ray diffraction as well as chemical phase analysis. The latter is based on the different solubility of the initial oxides and the compound formed (A., for example, are stable in acetic acid, while the oxides of rare earth elements dissolve well in it). Aluminates of rare earth elements have a high chemical resistance, depending on the temperatures of their pre-calcination; in water are steady at high temperatures (to 350 °C) under pressure. The best solvent for rare earth aluminates is hydrochloric acid. Rare earth aluminates are characterized by high refractoriness and characteristic coloration. Their densities range from 6500 to 7500 kg /m3.